In recent years, there has been much interest in exploiting the wave nature of electrons to achieve interference effects in microelectronic structures. This intense effort has been s purred by the achievement of Molecular Beam Epitaxial (MBE) layered semiconductor structures with very high electron mobilities at low temperatures, such as modulation-doped III-V heterostructures and, in particular, AlGaAs/GaAs heterostructures. In this semiconductor system, in particular, it is possible to build an entire device with active dimensions confined smaller than the electron's phase coherence length, i.e., 1 to 5 .mu.m, or less, depending on temperature, so that the phase of the electron wavefunction is preserved everywhere. Such a device is generally called a quantum structure. Under these circumstances, electron wave interference effects take place. In fact, electron wave interference in the AlGaAs/GaAs system has unequivocally been confirmed by the observation of the Aharanov-Bohm effect in very narrow rings and of coherent electron diffraction in periodic structures.
A quantum structure, such as a thin epitaxial film of narrow bandgap material, sandwiched between wider bandgap material, limits electrons to two degrees of freedom in the film and is referred to as a 2D Quantum Well or merely a Quantum Well. When the movement of electrons is further constricted in another direction, leaving only one degree of freedom, such as in a thin wire or waveguide, the structure is called a "Quantum Wire" or "Quantum Waveguide". One of the attributes of quantum wires or waveguides is the enhanced mobility of electrons in such structures caused by the reduction in scattering events resulting from one-dimensional confinement.
Goronkin et al., U.S. Pat. No. 4,769,683 issued Sept. 6, 1988, report the construction of a quasi 1-dimensional electron gas field-effect transistor in which 1-dimensional channel guide electrodes are arranged in parallel between source and drain electrodes for the purpose of reducing thermally generated noise.
Petroff et al. in "Toward Quantum Well Wires: Fabrication and Optical Properties", Appl. Phys. Lett. 41(7), October 1982, describe methods of fabricating quantum wires using molecular beam epitaxy (MBE) of GaAs and Ga.sub.1-x Al.sub.x As.
Ohtoshi et al. in U.S. Pat. No. 4,835,578 and Tsubaki et al., in Electronics Letters, V. 24, No. 20, September 1988, describe LED and FET semiconductor structures, respectively, having quantum wires.
Miller et al. in "Quantum Wires in InGaAs/InP Fabricated by Holographic Photolithography", Appl. Phys. Lett. 54(2), Jan. 9, 1989, described holographic techniques for fabrication of quantum wires.
Zheng et al. in "Gate-Controlled Transport in Narrow GaAs/Al.sub.x Ga.sub.1-x As Heterostructures", Physical Review, Vol. 34, No. 8, October 1986 and Hirayama et al. in "Conductance Characteristics of Ballistic One-Dimensional Channels Controlled by a Gate Electrode", Appl. Phys. Lett. 54(25), June 19, 1989 have conducted experimental studies into the transport phenomena of quantum wires.
The above represents a small sampling of the research and development effort being expended in this relatively new area of quantum physics related to ultra-small structures.